1. Technical Field
This Patent Disclosure relates generally to free running oscillators used with frequency locked control loops.
2. Related Art
Free running oscillators, in comparison to PLLs (phase locked loops), avoid the requirement for a PLL reference clock, and require significantly less area and power, even when implemented as an FLL (frequency locked loop) oscillator/clock. FLLs (incorporating free-running oscillators) are an acceptable alternative to a PLL in systems with sufficient tolerance for phase noise and frequency variation.
One application is a high frequency (300-3000 MHz) oscillator as the modulating clock in an OOK (on-off keying) based transmission and envelope detection receiving system. Since the receiver is an envelope detector, phase noise of the modulating clock is less important. Also, a certain variation in frequency is acceptable, since primarily, the receiver/detector responds to amplitude and not frequency.
Another application is a clocked power converter, where phase noise is not critical, and some error in frequency is acceptable.
Use of high frequency clocking in signal chain applications ordinarily requires taking into account EMI (electromagnetic interference) design considerations. Spread spectrum techniques can be used to spread the EMI energy over a certain frequency band, taking into account frequency deviation as a percentage of center frequency, and spread spectrum modulation frequency.